The invention relates to a connection and control unit for use in a user installation, comprising a "satellite decoder" having an input for television signals from a satellite, which decoder is capable of applying a DC control voltage to this input for the purpose of controlling the selection, by means of an external apparatus, of one of two signals, and which has a control current output for controlling a magnetic polarizer, said user installation being also connected to a television signal distribution system comprising an assembly of more than two separate satellite television signal sources each furnishing a plurality of channels which differ from each other by their frequencies, at least one unit referred to as "switching unit" having at least one output which is connected to the user installation via a cable, a plurality of inputs each connected to one of said separate sources, and switching means for selecting one of its inputs and connecting it to its output, said selection being made as a function of the characteristics of a control signal applied through the cable connecting the user installation to the switching unit.
The invention also relates to a system as defined hereinbefore.
All known systems authorize the user to make a selection from several broadcasts by tuning to one or the other carrier frequency. On the basis of frequencies ranging between 950 and 1750 MHz, for example in the case of signals received from a satellite via a decoder which supplies a signal at a frequency in this range of frequencies, with bands having a width of approximately 30 MHz, it is possible to distinguish 24 different channels. Nevertheless, this number is insufficient, considering that, for example a satellite assembly such as "Astra" has already more than 24 channels. This is the reason why a distribution system has been conceived in which a user can select a signal from a cable among a plurality of cables.
Such a system is known from the document "Second IEEE National Conference on Telecommunications, 5 Apr. 1989, pp. 128, 132" by D. McGovern, and is entitled "Satellite television receivers for the domestic market". The system described in this document has a branching element with four inputs (a 4-way splitter switch) which selects one of the inputs as a function of a control signal whose nature is not specified.